MAGNETIC-PROPERTIES OF FE-CR-BASED NANOCRYSTALLINE ALLOYS

FeCrCuNbSiB nanocrystalline alloys, with low fractions of the crystall ine phase (10-25%), have been studied by means of static magnetic meas urements and Mossbauer spectroscopy over a wide temperature range (4.2 -800 K). As a reference the temperature dependences of the hyperfine p arameters measured in ordered Fe-Si alloys were used. It has been show n that at temperatures close to the Curie point of the amorphous matri x the coercivity exhibits a maximum that corresponds to a kink in the thermal evolution of the hyperfine field of the crystalline phase. The se effects originate from the lessening of the interphase exchange int eractions at the ferro-paramagnetic phase transition of the amorphous matrix and superparamagnetic fluctuations of the magnetization in sing le-domain grains. A mechanism considering different energy contributio ns as well as their changes with temperature in such a mesoscopic syst em is discussed.